The invention relates generally to methods for reducing the amount of carbon monoxide in the mainstream smoke of a cigarette during smoking. More specifically, the invention relates to cut filler compositions, cigarettes, methods for making cigarettes and methods for smoking cigarettes that involve the use of oxyhydroxide compounds, which decompose during smoking to produce one or more products capable of acting as an oxidant for the conversion of carbon monoxide to carbon dioxide and/or as a catalyst for the conversion of carbon monoxide to carbon dioxide.
Various methods for reducing the amount of carbon monoxide in the mainstream smoke of a cigarette during smoking have been proposed. For example, British Patent No. 863,287 describes methods for treating tobacco prior to the manufacture of tobacco articles, such that incomplete combustion products are removed or modified during smoking of the tobacco article. In addition, cigarettes comprising absorbents, generally in a filter tip, have been suggested for physically absorbing some of the carbon monoxide. Cigarette filters and filtering materials are described, for example, in U.S. Reissue Pat. No. RE 31,700; U.S. Pat. No. 4,193,412; British Patent No. 973,854; British Patent No. 685,822; British Patent No. 1,104,993 and Swiss patent 609,217. However, such methods are usually not completely efficient.
Catalysts for the conversion of carbon monoxide to carbon dioxide are described, for example, in U.S. Pat. Nos. 4,317,460, 4,956,330; 5,258,330; 4,956,330; 5,050,621; and 5,258,340, as well as in British Patent No. 1,315,374. The disadvantages of incorporating a conventional catalyst into a cigarette include the large quantities of oxidant that need to be incorporated into the filter to achieve considerable reduction of carbon monoxide. Moreover, if the ineffectiveness of the heterogeneous reaction is taken into account, the amount of the oxidant required would be even larger.
Metal oxides, such as iron oxide have also been incorporated into cigarettes for various purposes. See, for example, International Publications WO 87/06104 and WO 00/40104, as well as U.S. Pat. Nos. 3,807,416 and 3,720,214. Iron oxide has also been proposed for incorporation into tobacco articles, for a variety of other purposes. For example, iron oxide has been described as particulate inorganic filler (e.g. U.S. Pat. Nos. 4,197,861; 4,195,645; and 3,931,824), as a coloring agent (e.g. U.S. Pat. No. 4,119,104) and in powder form as a burn regulator (e.g. U.S. Pat. No. 4,109,663). In addition, several patents describe treating filler materials with powdered iron oxide to improve taste, color and/or appearance (e.g. U.S. Pat. Nos. 6,095,152; 5,598,868; 5,129,408; 5,105,836 and 5,101,839). However, the prior attempts to make cigarettes incorporating metal oxides, such as FeO or Fe2O3 have not led to the effective reduction of carbon monoxide in mainstream smoke.
Despite the developments to date, there remains a need for improved and more efficient methods and compositions for reducing the amount of carbon monoxide in the mainstream smoke of a cigarette during smoking. Preferably, such methods and compositions should not involve expensive or time consuming manufacturing and/or processing steps. More preferably, it should be possible to catalyze or oxidize carbon monoxide not only in the filter region of the cigarette, but also along the entire length of the cigarette during smoking.
The invention provides cut filler compositions, cigarettes, methods for making cigarettes and methods for smoking cigarettes that involve the use of an oxyhydroxide compound, which is capable of decomposing to form at least one product capable of acting as an oxidant for the conversion of carbon monoxide to carbon dioxide and/or as a catalyst for the conversion of carbon monoxide to carbon dioxide.
One embodiment of the invention relates to a cut filler composition comprising tobacco and an oxyhydroxide compound, wherein during combustion of the cut filler composition, the oxyhydroxide compound is capable of decomposing to form at least one product capable of acting as an oxidant for the conversion of carbon monoxide to carbon dioxide and/or as a catalyst for the conversion of carbon monoxide to carbon dioxide.
Another embodiment of the invention relates to a cigarette comprising a tobacco rod, wherein the tobacco rod comprises a cut filler composition comprising tobacco and an oxyhydroxide compound. During smoking of the cigarette, the oxyhydroxide compound is capable of decomposing to form at least one product capable of acting as an oxidant for the conversion of carbon monoxide to carbon dioxide and/or as a catalyst for the conversion of carbon monoxide to carbon dioxide. The cigarette preferably comprises from about 5 mg to about 200 mg of the oxyhydroxide compound per cigarette, and more preferably from about 40 mg to about 100 mg of the oxyhydroxide compound per cigarette.
A further embodiment of the invention relates to a method of making a cigarette, comprising (i) adding an oxyhydroxide compound to a cut filler, wherein the oxyhydroxide compound is capable of decomposing during the smoking of the cigarette to form at least one product capable of acting as an oxidant for the conversion of carbon monoxide to carbon dioxide and/or as a catalyst for the conversion of carbon monoxide to carbon dioxide; (ii) providing the cut filler comprising the oxyhydroxide compound to a cigarette making machine to form a tobacco rod; and (iii) placing a paper wrapper around the tobacco rod to form the cigarette. The cigarette thus produced preferably comprises from about 5 mg to about 200 mg of the oxyhydroxide compound per cigarette, and more preferably from about 40 mg to about 100 mg of the oxyhydroxide compound per cigarette.
Yet another embodiment of the invention relates to a method of smoking the cigarette described above, which involves lighting the cigarette to form smoke and inhaling the smoke, wherein during the smoking of the cigarette, the oxyhydroxide compound is capable of decomposing to form at least one product capable of acting as an oxidant for the conversion of carbon monoxide to carbon dioxide and/or as a catalyst for the conversion of carbon monoxide to carbon dioxide.
In a preferred embodiment of the invention, the oxyhydroxide compound is capable of decomposing to form at least one product capable of acting as both an oxidant for the conversion of carbon monoxide to carbon dioxide and as a catalyst for the conversion of carbon monoxide to carbon dioxide. Preferred oxyhydroxide compounds include, but are not limited to: FeOOH, AlOOH, TiOOH, and mixtures thereof, with FeOOH being particularly preferred. Preferably, the oxyhydroxide compound is capable of decomposing to form at least one product selected from the group consisting of Fe2O3, Al2O3, TiO2, and mixtures thereof. Preferably, the product formed from the decomposition of the oxyhydroxide during combustion of the cut filler composition is present in an amount effective to convert at least 50% of the carbon monoxide to carbon dioxide.
In yet another preferred embodiment, the oxyhydroxide compound and/or the product formed from the decomposition of the oxyhydroxide during combustion of the cut filler composition is in the form of nanoparticles, preferably having an average particle size less than about 500 nm, more preferably having an average particle size less than about 100 nm, more preferably having an average particle size less than about 50 nm, and most preferably having an average particle size less than about 5 nm.